_Petroxolinum Hydrargyri (Petrox. Hydrarg.), Mercury Petroxolin, N.F._ (Mercury Petrox).--Mercury (30%) in hydrous wool fat, oleic acid and solid petroxolin. _*Unguentum Hydrargyri (Ung. Hydrarg.), Mercurial Ointment, U.S.P._--Metallic mercury (about 50%) and oleate of mercury (2%) with prepared suet and benzoinated lard. USES: Especially to secure the systemic effects of mercury by inunction. _*Unguentum Hydrargyri Dilutum (Ung. Hydrarg. Dil.), Diluted Mercurial Ointment, U.S.P._ (Blue Ointment, Hydrargyri Unguentum P.I.).--Mercurial ointment (60%) equivalent to about 30 per cent. of metallic mercury, with petrolatum. USES: Especially in pediculosis. =*Hydrargyrum Ammoniatum (Hydrarg. Ammon.), Ammoniated Mercury, U.S.P.= (White Precipitate).--Mercurammonium chloride, HgNH{2}Cl, corresponding to about 79 per cent. of Hg. White, odorless lumps or powder, with an earthy, afterward styptic and metallic taste. Insoluble in water or alcohol. ACTION AND USES: The ointment is extensively used as a cutaneous antiseptic especially for impetigo contagiosa and other pustular dermatoses and ringworm of the scalp. Also used for removing scales of psoriasis. It may cause salivation. DOSAGE: From 2 to 10 per cent. ointment. _*Unguentum Hydrargyri Ammoniati (Ung. Hydrarg. Ammon.), Ointment of Ammoniated Mercury, U.S.P._ (White Precipitate Ointment).--Ammoniated mercury (10%) in white petrolatum and hydrous wool fat. =Hydrastina (Hydrastina), Hydrastine, U.S.P.=--An alkaloid obtained from hydrastis or prepared synthetically. White crystals or powder. Almost insoluble in water, soluble in alcohol (1:170). ACTION AND USES: Used in the treatment of urethral and vesical catarrh and as a systemic hemostatic, especially in excessive menstruation. Its efficiency and the mechanism of its action are doubtful. DOSAGE: 0.01 Gm. or 1/6 grain (U.S.P.). =Hydrastinae Hydrochloridum (Hydrastin. Hydrochl.), Hydrastine Hydrochloride, U.S.P.= (Hydrastine Chloride). White, odorless, bitter powder. Very soluble in water and in alcohol. ACTION AND USES: Those of hydrastine. DOSAGE: 0.01 Gm. or 1/6 grain (U.S.P.). _Liquor Hydrastinae Compositus (Liq. Hydrastin. Co.), Compound Solution of Hydrastine, N.F._ (Colorless Hydrastine Solution).--Hydrastine hydrochloride (0.3%), aluminum chloride, calcium chloride, and magnesium chloride (each 0.3%), potassium chloride (0.1%) in glycerin and water. USES: Complex and irrational astringent. DOSAGE: 4 Cc. or 1 fluidrachm (N.F.). =Hydrastininae Hydrochloridum (Hydrastinin. Hydrochl.), Hydrastinine Hydrochloride, U.S.P.= (Hydrastinine Chloride).--The hydrochloride of hydrastinine, an alkaloid obtained synthetically from hydrastine. Yellowish, odorless crystals or powder. Soluble in chloroform (1:195); very soluble in water and alcohol.